When Steve Jobs announced iCloud back in early June, one of the big features was iTunes Match. It was the only component of iCloud to directly tackle iTunes’ musical roots. But when iOS 5 brought the official iCloud launch last month, iTunes Match was left out for unknown reasons. The service is available now via the iTunes 10.5.1 update.

There are some key differences between iTunes Match and other cloud music options. Like rivals Amazon MP3 and Google Music beta, Apple’s service lets you store your entire music collection in the cloud. But while the competing services require you to upload every song to their servers (a weeklong process for some), iTunes Match simply scans your collection and instantly matches their existing files to your account. The only uploading that is required is for obscure or unlicensed tracks that aren’t already in iTunes.

There is, however, one more key difference that could make iTunes Match a less than desirable cloud music service. Unlike Google’s and Amazon’s cloud players, iTunes Match does not stream — so you’ll be required to download anything you want to listen to. So while you can hypothetically have your entire music collection on your iPhone, you will pay for it in flash storage.

It will be interesting to see how iTunes Match catches on with music fans. The last year has seen an increased interest in subscription services like Spotify, Rdio, Rhapsody, and (the questionably legal) Grooveshark. While these services typically cost more than iTunes Match ($10/month next to $25/yr for Apple’s service), their libraries are impressive, and no precious mobile storage is needed. Deals with Facebook have only increased their popularity, so Apple may have some stiff competition there.

One thing about iTunes Match that raised some eyebrows is that it can’t differentiate between a user’s pirated and legally obtained music. So if Joe BitTorrent User has a library full of pirated albums, a quick scan is all it will take to add it to his iTunes Match account. One way that Apple is combating this is by blocking users whose libraries contain more than 25,000 songs which weren’t purchased from Apple. It’s an interesting approach, and it will surely block some of the most hardcore music fans along with the targeted illegal downloaders.

If iTunes Match is the service for you, then you can download the latest version of iTunes and sign up now. The update may not be showing up as an update yet, but you can download it at the link below.